The solar generators mounted on spacecraft, for example satellites, generally comprise, an array of solar cells electrically connected to one another and to the satellite, the solar cells, covering the surface of support panels being suitable for transforming the solar energy into electrical energy transmitted to the electrical equipment items of the satellite. The solar cells can be formed on a number of rigid solar panels or on a flexible support, for example a flexible membrane, the thickness of which is very much thinner than the thickness of the rigid solar panels. In effect, a flexible solar generator generally consists of a flexible support comprising a front face on which solar cells are mounted, each solar cell being provided with a glass protection window (cover glass), a rear face on which are formed electrical conductors and at least one layer of insulating material, for example Kapton, situated between the solar cells and the electrical conductors.
As represented in the electrical circuit diagram of FIG. 1, the solar cells formed on the flexible support 10 and situated on a same string of the solar generator are generally electrically connected in series, each string 11 comprising two ends 12, 13 with respectively positive and negative polarity. The ends 12, 13 with positive, respectively negative, polarity of several strings are then electrically connected to one another to form several different sections 15, 16, each section consisting of a set of several strings electrically connected in parallel. Two sections each consisting of three strings connected in parallel are represented in FIG. 1, but, generally, the number of strings per section and the number of sections are greater. Each section 15, 16 is then linked to the satellite 20 by two electrical power conductors 15a, 15b, 16a, 16b respectively of positive polarity and negative polarity, also called electrical transfer conductors, dedicated to transferring electrical power generated by the section to the satellite. The electrical transfer conductors 15a, 15b, 16a, 16b dedicated to the sections 15, 16 are generally formed under the solar cells, on the rear face of the flexible support 10 of the solar generator. Since the different sections are formed alongside one another in a same longitudinal direction of the solar generator, the electrical power conductors dedicated to the different sections pass under the solar cells of the neighboring sections and run under all the wing of the solar generator 10 before being connected to the satellite 20. For example, in FIG. 1, the electrical transfer conductors 15a, 15b of the section 15 run under the solar cells of the section 16.
The problem is that, in the case of the flexible solar generators, the distance separating the solar cells mounted on a front face of the flexible support and the electrical power conductors mounted on a rear face of the flexible support is very small, that is to say less than a millimetre. This small distance makes the solar generators very sensitive to impacts from celestial objects, in particular to impacts from debris and from micrometeorites. In effect, the impacts, for example, from debris or from micrometeorites can locally pierce one or more solar cells as well as the insulating materials and the power conductors situated under the solar cell. The impact creates a plasma bubble which, when the electrical voltage between the impacted solar cell and the electrical conductor is sufficient, for example greater than 50 Volts, can generate an electrical arc 14 between said impacted solar cell and the electrical conductor placed under that solar cell. If the electrical current available at the point of the impact is sufficiently high, for example greater than 1.5 Ampere, the electrical arc can be self-sustaining, which has the effect of creating a permanent short circuit in a section of the solar generator and a definitive loss of a part of the electrical power.
To protect the solar cells against any discharge currents originating from the other strings of the section, each string is generally provided, at its positive polarity end, with a blocking diode 17 making it possible to insulate the strings from one another and to limit the intensity of the electrical current in each string to a value less than 1.5 Ampere. However, since these blocking diodes are located on the flexible support, as close as possible to the solar cells, they provide protection against the electrical arcs generated between solar cells of neighboring strings but do not protect against electrical arcs generated between the solar cells and the electrical transfer conductors, in particular the electrical transfer conductors that have a positive polarity, which run under the solar cells and which are connected at the output of a section of the solar generator. Now, at the point of impact, the voltage of an electrical transfer conductor having a positive polarity can be very much greater than the voltage of the cell impacted, for example for a string comprising 50 solar cells connected in series, the voltage of an electrical transfer conductor having a positive polarity can reach 100 Volts whereas the voltage of the negative polarity end of the first cell of a string is equal to 0 Volt. Furthermore, the intensity of the electrical current circulating in an electrical transfer conductor connected at the output of a section is high, generally very much greater than 1.5 Ampere. When a micrometeorite passes through the solar generator and makes a hole in a solar cell and in the insulating material between the solar cell and an electrical transfer conductor with positive polarity situated under the solar cell, an electrical arc is created and is self sustaining between the electrical power conductor and the impacted solar cell. A short circuit is then generated between the impacted cell and the electrical transfer conductor 15a with positive polarity which passes under said impacted cell. An electrical arc current I then circulates from the electrical transfer conductor 15a with positive polarity to an electrical transfer conductor 16b with negative polarity linked to the negative end of the string of solar cells in which the impact has occurred. Since the electrical transfer conductors with negative polarity are all linked together in the satellite 20, the electrical arc current I returns in the reverse direction, via an electrical transfer conductor with negative polarity, into the electrical circuit of the section 15 which passes under the impacted cell. Said section 15 is then short circuited and can no longer supply power to the solar generator. This loss of power corresponding to the loss of a complete section 15 of the solar generator is prejudicial to the electrical power supply for the equipment items on board the satellite.
To avoid electrical arcs being created between a solar cell and an electrical transfer conductor, it is possible to have the transfer conductors run on the edges of the solar generator instead of having them run on the rear face, under the solar cells. However, the electrical transfer conductors also provide a shielding role for the rear face of the solar generator against radiations, notably electron fluxes and photon fluxes, which degrade the electrical performance levels of the solar cells causing the available electrical power to be reduced. Consequently, if the electrical transfer conductors are moved to the edges of the solar generator, they can no longer ensure the shielding role and it is then necessary to add a specific shielding device to protect the rear face of the solar generator, which increases the weight of the solar generator.